FXUS64 KHUN 181548 AAA AFDHUN AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE HUNTSVILLE AL 1048 AM CDT TUE MAR 18 2014 .UPDATE... MAINLY ADJUSTED CLOUD COVER AND TEMPS FOR TODAY. && .DISCUSSION... A SOLID DECK OF STRATUS CONTINUES TO BLANKET THE SKY ACROSS THE TN VALLEY THIS MORNING. AREA AND REGIONAL OBSERVATIONS INDICATE CLOUD BASES ARE AROUND 1 TO 1.5 KFT AND A SYNTHESIS OF SATELLITE DATA/IMAGERY AND MODEL ANALYSES SUGGESTS THE CLOUD TOPS ARE ARND 4-5 KFT. THE FCST CHALLENGE FOR TODAY IS DETERMINING WHETHER OR NOT THESE CLOUDS WILL BE MAINTAINED ACROSS THE AREA...WITH CONTINUING IMPACTS TO INSOLATION...SFC TEMPS...AND THE OTHER EXPECTED IMPACTS TO AVIATION. WITH LOW-LVL FLOW IN THE CLOUD BEARING LAYER SLIGHTLY CONVERGENT AND FROM THE E-SE...AND WITH LITTLE TEMP OR DRY AIR ADVECTION...IT IS LOOKING MORE LIKELY THAT CLOUDS WILL LINGER FOR MOST OF THE DAY...PARTICULARLY IN THE EAST. THE LATEST SATELLITE IMAGERY LENDS SUPPORT FOR THIS. ISENTROPIC ANALYSIS INDICATES CONTINUED SHALLOW LIFT IN THE CLOUD LAYER MAINLY BTWN 925-830 MB...LENDING MODEL EVIDENCE TO SUPPORT MAINTENANCE OF THE CLOUD DECK AND SOME POTENTIAL FOR PATCHY -DZ. WITH ALL OF THAT SAID...SKY COVER WAS INCREASED FOR THIS AFTERNOON...AND TEMPS WERE LOWERED FOR MOST LOCATIONS (ALTHOUGH THEY WERE RAISED A LITTLE FOR A FEW LOCATIONS IN THE EAST). THE RESULT IS...HIGH TEMPS MAINLY IN THE 50S FOR TODAY...WITH CLOUDS LIKELY LINGERING INTO THE LATE AFTERNOON AND THE EARLY EVENING. THE LONE CAVEAT FOR THIS CLOUDIER SCENARIO RESTS IN THE POTENTIAL FOR HORIZONTAL AND VERTICAL MIXING OF DRIER AIR ON THE BORDER OF THE CLOUD DECK. CURRENTLY...THE PRESSURE GRADIENT IS INCREASING RAPIDLY ACROSS THE MID-MISSISSIPPI VALLEY IN RESPONSE TO A SFC LOW MOVING ACROSS THE SOUTHERN PLAINS. A DIGGING UPR TROUGH IN THE CENTRAL HIGH PLAINS WILL CONTINUE TO CAUSE DEEPENING OF THE SFC LOW AND FORCE WINDS ALOFT (AND ABOVE THE CLOUD LAYER) TO BACK TO THE SW THIS AFTERNOON. EROSION OF THE CLOUD DECK TO OUR WEST ACROSS MISS/TENN MAY BE RAPID WITH STRONG WAA ALOFT AND INCREASING SW WIND FLOW. A DECENT TEMP GRADIENT WILL LIKELY DEVELOP ALONG THE EDGE OF THE CLOUD DECK AND IF IT MOVES INTO NW ALABAMA...THEN TEMPS MAY IN FACT REACH THE 60S. NEVERTHELESS..THIS UPDATE WILL REFLECT A CLOUDIER/COOLER SCENARIO FOR NOW. KDW && .AVIATION... /ISSUED 651 AM CDT TUE MAR 18 2014/ FOR 12Z TAFS...THICK STRATUS CONTINUES TO BLANKET THE REGION THIS MORNING...WITH IFR CIGS LIKELY TO PERSIST THRU 18/15Z AT BOTH MSL/HSV. VSBY REDUCTIONS TO 3-5 SM IN BR APPEAR TO BE LIMITED TO THE ERN HALF OF NORTH ALABAMA...AND WILL ONLY INCLUDE THIS IN TAF FOR HSV. SE FLOW WILL BEGIN TO INCREASE BY MID/LATE MORNING AS A STRONGER SFC LOW DEVELOPS OVER THE CENTRAL PLAINS...AND THIS WILL LEAD TO GRADUAL IMPROVEMENT IN CIGS -- ESPECIALLY THIS AFTN. HOWEVER...AS NOCTURNAL LOW-LEVEL JET STRENGTHENS THIS EVENING...EXPECT STRATUS DECK TO LOWER TO AROUND 1500 FT ONCE AGAIN. SFC WINDS WILL INCREASE TO ARND 10 KTS AND VEER FROM SE TO SSE THRU THE PERIOD. HAVE INCLUDED LLWS BEGINNING AT 19/03Z AS FLOW OFF THE SFC SHOULD STRENGTHEN TO ARND 35 KTS BY THIS TIME. 70/DD && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WEATHER.GOV/HUNTSVILLE.
Posted on: Tue, 18 Mar 2014 15:49:38 +0000
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